/**
 * 	@filename :
 * 		test_threads_pool.c
 * 
 * 	@note :
 *
 **/

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <pthread.h>
#include <assert.h>

/*
*线程池里所有运行和等待的任务都是一个CThread_worker
*由于所有任务都在链表里，所以是一个链表结构
*/
typedef struct worker {
	/*回调函数，任务运行时会调用此函数，注意也可声明成其它形式*/
	void *(*process) (void *arg);
	void *arg;/*回调函数的参数*/
	struct worker *next;

} CThread_worker;


/*线程池结构*/
typedef struct {
	pthread_mutex_t queue_lock;
	pthread_cond_t queue_ready;
	
	/*链表结构，线程池中所有等待任务*/
	CThread_worker *queue_head;
	
	/*是否销毁线程池*/
	int shutdown;
	pthread_t *threadid;
	/*线程池中允许的活动线程数目*/
	int max_thread_num;
	/*当前等待队列的任务数目*/
	int cur_queue_size;

} CThread_pool;


int pool_add_worker (void *(*process) (void *arg), void *arg);
void *thread_routine (void *arg);

static CThread_pool *pool = NULL;

void
pool_init (int max_thread_num)
{
	pool = (CThread_pool *) malloc (sizeof (CThread_pool));
	
	pthread_mutex_init (&(pool->queue_lock), NULL);
	pthread_cond_init (&(pool->queue_ready), NULL);
	
	pool->queue_head = NULL;
	
	pool->max_thread_num = max_thread_num;
	pool->cur_queue_size = 0;
	
	pool->shutdown = 0;
	
	pool->threadid =
		(pthread_t *) malloc (max_thread_num * sizeof (pthread_t));
		
	int i = 0;
	for (i = 0; i < max_thread_num; i++) {
		pthread_create (&(pool->threadid[i]), NULL, thread_routine,
			 NULL);
	}
}


/*向线程池中加入任务*/
int
pool_add_worker (void *(*process) (void *arg), void *arg)
{
	/*构造一个新任务*/
	CThread_worker *newworker =
		(CThread_worker *) malloc (sizeof (CThread_worker));
	newworker->process = process;
	newworker->arg = arg;
	newworker->next = NULL;/*别忘置空*/
	
	pthread_mutex_lock (&(pool->queue_lock));
	/*将任务加入到等待队列中*/
	CThread_worker *member = pool->queue_head;
	if (member != NULL) {
		while (member->next != NULL) {
			member = member->next;
		}
		member->next = newworker;
	} else {
		pool->queue_head = newworker;
	}
	
	assert (pool->queue_head != NULL);
	
	pool->cur_queue_size++;
	/*
	 好了，等待队列中有任务了，唤醒一个等待线程；
	 注意如果所有线程都在忙碌，这句没有任何作用
	*/
	pthread_cond_signal (&(pool->queue_ready));	
	pthread_mutex_unlock (&(pool->queue_lock));
	
	return 0;
}


/*销毁线程池，等待队列中的任务不会再被执行，但是正在运行的线程会一直
把任务运行完后再退出*/
int
pool_destroy ()
{
	if (pool->shutdown) {
		return -1;/*防止两次调用*/
	}
	
	pool->shutdown = 1;
	
	/*唤醒所有等待线程，线程池要销毁了*/
	pthread_cond_broadcast (&(pool->queue_ready));
	
	/*阻塞等待线程退出，否则就成僵尸了*/
	int i;
	for (i = 0; i < pool->max_thread_num; i++) {
		pthread_join (pool->threadid[i], NULL);
	}
	
	free (pool->threadid);

	/*销毁等待队列*/
	CThread_worker *head = NULL;
	while (pool->queue_head != NULL) {
		head = pool->queue_head;
		pool->queue_head = pool->queue_head->next;
		free (head);
	}
	 
	/*条件变量和互斥量也别忘了销毁*/
	pthread_mutex_destroy(&(pool->queue_lock));
	pthread_cond_destroy(&(pool->queue_ready));
	
	free (pool);
	/*销毁后指针置空是个好习惯*/
	pool=NULL;
	 
	return 0;
}


void *
thread_routine (void *arg)
{
	printf ("starting thread 0x%x\n", (unsigned int)pthread_self ());
	
	while (1) {
		pthread_mutex_lock (&(pool->queue_lock));
		/*如果等待队列为0并且不销毁线程池，则处于阻塞状态; 注意
		pthread_cond_wait是一个原子操作，等待前会解锁，唤醒后会加锁*/
		while (pool->cur_queue_size == 0 && !pool->shutdown) {
			printf ("thread 0x%x is waiting\n", (unsigned int)pthread_self ());
			pthread_cond_wait (&(pool->queue_ready), &(pool->queue_lock));
		}
		
		/*线程池要销毁了*/
		if (pool->shutdown) {
			/*遇到break,continue,return等跳转语句，千万不要忘记先解锁*/
			pthread_mutex_unlock (&(pool->queue_lock));
			printf ("thread 0x%x will exit\n", (unsigned int)pthread_self ());
			pthread_exit (NULL);
		}
		
		printf ("thread 0x%x is starting to work\n", (unsigned int)pthread_self ());
		
		/*assert是调试的好帮手*/
		assert (pool->cur_queue_size != 0);
		assert (pool->queue_head != NULL);
		
		/*等待队列长度减去1，并取出链表中的头元素*/
		pool->cur_queue_size--;
		CThread_worker *worker = pool->queue_head;
		pool->queue_head = worker->next;
		pthread_mutex_unlock (&(pool->queue_lock));
		
		/*调用回调函数，执行任务*/
		(*(worker->process)) (worker->arg);
		free (worker);
		worker = NULL;
	}
	 
	/*这一句应该是不可达的*/
	pthread_exit (NULL);
}

void *
myprocess (void *arg)
{
	printf ("threadid is 0x%x, working on task %d\n", (unsigned int)pthread_self (), *(int *) arg);
	sleep (1);/*休息一秒，延长任务的执行时间*/
	 
	return NULL;
}

int
main (int argc, char **argv)
{
	pool_init (3);/*线程池中最多三个活动线程*/
	
	/*连续向池中投入10个任务*/
	int *workingnum = (int *) malloc (sizeof (int) * 10);
	int i;
	for (i = 0; i < 10; i++)
	{
		workingnum[i] = i;
		pool_add_worker (myprocess, &workingnum[i]);
	}
	/*等待所有任务完成*/
	sleep (5);
	/*销毁线程池*/
	pool_destroy ();
	
	free (workingnum);
	
	return 0;
}
